Fluid testing

ABSTRACT

A fluid testing device may include a fluid interaction element and a fluid chamber to contain a fluid to be sensed by the fluid interaction element. The fluid chamber may form a first gap through which fluid is to be wicked to a second gap that is opposite the fluid interaction element and less than the first gap.

BACKGROUND

Fluid testing is used in a variety of fields including healthcare, lifesciences, environmental sciences, chemistry, and food safety, amongothers. Examples of fields where testing is employed include biomedicaltesting, molecular testing, industrial testing, food testing and labtesting. Such testing is often performed by sensing the characteristicsof small fluid samples taken from or derived from the subject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of portions of an example fluid testingdevice in the form of a fluid testing tool.

FIG. 2 is a flow diagram of an example fluid testing method.

FIG. 3 is a perspective view of an example fluid testing stick.

FIG. 4 is a sectional view of the fluid testing stick of FIG. 3 takenalong line 4-4.

FIG. 5 is a sectional view of an example fluid testing stick.

FIG. 6 is a sectional view of an example fluid testing stick.

FIG. 7 is a sectional view of an example fluid testing stick.

FIG. 8 is a sectional view of an example fluid testing stick.

FIG. 9 is a sectional view of an example fluid testing stick.

FIG. 10 is a sectional view of an example fluid testing stick.

FIG. 11 is a sectional view of an example fluid testing stick.

FIG. 12 is a sectional view of an example fluid testing stick.

FIG. 13 is an end view of an example fluid testing stick.

FIG. 14 is a sectional view of the fluid testing stick of FIG. 13 takenalong line 14-14.

FIG. 15 is an end view of an example fluid testing stick.

FIG. 16 is a sectional view of the fluid testing stick of FIG. 15 takenalong line 16-16.

FIG. 17 is a sectional view of an example fluid testing stick.

FIG. 18 is a top view of an example fluid testing stick.

FIG. 19 is a sectional view of the fluid testing stick of FIG. 18 takenalong line 19-19.

FIG. 20 is a front view of an example fluid testing stick.

FIG. 21 is a perspective view of an example lid of the fluid testingstick of FIG. 20.

FIG. 22 is a perspective view of the fluid testing stick of FIG. 20 isinserted within an example receptacle.

FIG. 23 is a sectional view of the fluid testing stick inserted withinthe example receptacle with the receptacle also containing a samplefluid.

FIG. 24 is a front view illustrating an example electronic device forcommunicating with the fluid testing stick of FIG. 20.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements. The figures are not necessarilyto scale, and the size of some parts may be exaggerated to more clearlyillustrate the example shown. Moreover, the drawings provide examplesand/or implementations consistent with the description; however, thedescription is not limited to the examples and/or implementationsprovided in the drawings.

DETAILED DESCRIPTION OF EXAMPLES

Disclosed herein are fluid testing devices in the form of fluid testingtools, fluid testing methods and fluid testing devices in the form offluid testing sticks that facilitate testing or diagnostics using smallfluid samples. The disclosed fluid testing tools, testing methods andtesting fluid interaction sticks facilitate precise fluid manipulation,interaction and/or property sensing on a microfluidic strip or chip.Such testing tools facilitate the preparation of a fluid sample and/orthe sensing of the fluid sample at a low cost and with a low degree ofcomplexity.

The disclosed fluid testing tools, testing methods and fluid testingsticks utilize wicking or capillary forces to draw or pull a samplefluid into a first gap of a fluid chamber and then draw the sample fluidinto a second smaller gap that extends adjacent a fluid interactionelement. The larger dimension of the first gap facilitates fasterwicking of the fluid into the fluid testing tool or testing fluidinteraction stick. The smaller dimension of the second gap results in asmaller volume of the fluid sample being positioned directly adjacentthe fluid interaction element such that the fluid sample may be moreprecisely manipulated and more quickly interacted upon for enhanceddiagnosis.

In some implementations, the smaller dimensions of the second gap mayprovide enhanced thermal control of fluid in close contact with thefluid interaction element or elements. The large amount of surface areaof the fluid interaction element relative to the small fluid volumeprovides more direct fluid contact to provide enhanced “zonal” controlof fluid temperature, fluid dynamics and/or property sensing. In someimplementations, the fluid testing tools, methods and fluid testingsticks facilitate parallel or serial processing of fluids with a singlemicrochip or multiple microchips integrated into a single microfluidicsconsumable.

Disclosed herein is an example fluid testing tool that includes a fluidinteraction element; and a fluid chamber to contain a fluid to be sensedby the fluid interaction element. The fluid chamber forms a first gapthrough which fluid is to be wicked to a second gap that is opposite thefluid interaction element and less than the first gap.

Disclosed herein is an example fluid testing method that includeswicking fluid into a first gap in a chamber and interacting with thefluid with a fluid interaction element while the fluid is in a secondgap that is adjacent the first gap in the chamber and less than thefirst gap.

Disclosed herein is an example fluid testing stick comprising a firstend supporting a controller and a second end forming a fluid interactor.The fluid interactor includes a fluid interaction element under controlof the controller and a fluid chamber to contain a fluid to be sensed bythe fluid interaction element. The fluid chamber forms a first gapthrough which fluid is to be wicked to a second gap that is opposite thefluid interaction element and less than the first gap.

FIG. 1 is a schematic diagram of an example fluid testing tool 20.Testing tool 20 facilitates precise fluid manipulation, interactionand/or property sensing on a microfluidic strip or chip. Testing tool 20facilitates the preparation of a fluid sample and/or the sensing of thefluid sample at a low cost and with a low degree of complexity. Testingtool 20 includes fluid interaction element 24 and fluid chamber 28.

Fluid interaction element (FIE) 24 includes at least one element thatinteracts with portions of a fluid sample introduced into chamber 28. Inone implementation, fluid interaction element 24 thermally interactswith adjacent portions of an introduced fluid sample. For example, inone implementation, fluid interaction element 24 may apply heat to theadjacent portions of the fluid sample. In some implementations, fluidinteraction element 24 may thermally cycle the fluid sample, such as innucleic acid testing or a polymerase chain reaction (PCR) procedure. Insuch an implementation, fluid interaction element 24 may comprise athermal resistor which outputs heat in response to the application ofelectrical current.

In other implementations, fluid interaction element 24 may interact withthe adjacent portions of the fluid sample in other fashions. Forexample, in other implementations, fluid action element 24 may compriseat least one light emitter. In one implementation, fluid interactionelement 24 may comprise a surface that interacts with the fluid sampleto facilitate sensing of the fluid sample. For example, in oneimplementation, fluid interaction element 24 may comprise a plasmonicsurface that facilitates surface enhanced Raman spectroscopy. In oneimplementation, fluid interaction element 24 may comprise an array offlexible nano pillars or nano fingers having plasmonic tips.

In another implementation, fluid interaction element 24 may comprise anoptical sensor, a sensor that senses light. For example, in oneimplementation, fluid interaction element 24 may comprise a photodiodeor photodiode array. A fluid interaction element 24 in the form of thefluid diode may be utilized to sense or detect various light reflected,generated or otherwise emitted from a sample. In yet otherimplementations, fluid interaction element 24 may comprise a fluidpresence sensor which may indicate the presence or movement of fluid.

Fluid chamber 28 includes a body forming an internal volume extendingabout and adjacent to fluid interaction element 24. Fluid chamber 28contains fluid to be interacted upon by fluid interaction element 24. Asshown by FIG. 1, fluid chamber 28 forms a first gap 30 through whichfluid is wicked to a second gap 32 that is opposite the fluidinteraction element 24 and less than the first gap 30. Although gap 32is illustrated as having a uniform size or dimension across fluidinteraction element 24, in other implementations, gap 32 may have avarying dimension, a dimension that changes with respect to differentportions of fluid interaction element 24. Likewise, gap 30 may benon-uniform. As will be described hereafter, such as with respect toFIGS. 4-12, the gaps 30 and 32 may be formed by various structures orsurfaces that form or define the interior volume of chamber 28.

Testing tool 20 operates by pulling or drawing a sample fluid into gap30 of a fluid chamber 28 and then drawing the sample fluid into thesecond smaller gap 32 that extends adjacent fluid interaction element24. In one implementation, gap 32 is no greater than 1 mm while gap 30is at least 50% larger than gap 32. In one implementation, gap 30 is atleast 1.5 mm. The larger dimension of the gap 30 facilitates fasterwicking of the fluid into chamber 28. The smaller dimension of gap 32results in a smaller volume of the fluid sample being positioneddirectly adjacent the fluid interaction element 28 such that the fluidsample may be more precisely manipulated and more quickly interactedupon for enhanced diagnosis.

In some implementations, the smaller dimensions of gap 32 may provideenhanced thermal control of fluid interactor close contact with thefluid interaction 24. The high surface area of the fluid interactionelement 24 provides more direct fluid contact to provide enhanced“zonal” control of fluid temperature, fluid dynamics and/or propertysensing. In some implementations, fluid testing tool 20 facilitatesparallel or serial processing of fluids with a single microchip ormultiple microchips integrated into a single microfluidics consumable.

FIG. 2 is a flow diagram of an example fluid testing method 100. Method100 facilitates the preparation of a fluid sample and/or the sensing ofthe fluid sample at a low cost and with a low degree of complexity. Asindicated by block 104, fluid is wicked into a first gap, such as gap 30in a fluid chamber, such as fluid chamber 28 described above. Asindicated by block 108, the fluid is interacted upon with a fluidinteractor, such as fluid interaction element 24, while the fluid is ina second gap, such as gap 32, that is adjacent the first gap in thechamber and that is less than the first gap. In one implementation, gap32 is no greater than 1 mm while gap 30 is at least 50% larger than gap32. In one implementation, gap 30 is at least 1.5 mm.

The larger first gap facilitates faster wicking of the fluid into thechamber. The smaller dimension of the second gap results in a smallervolume of the fluid sample being positioned directly adjacent the fluidinteraction element 28 such that the ratio of the surface area of fluidinteraction element 24 to the volume adjacent the fluid interactionelement (the surface to volume ratio) is larger such that the fluidsample may be more precisely manipulated and more quickly interactedupon for enhanced results.

FIGS. 3 and 4 illustrate an example fluid testing tool in the form of anexample fluid testing stick 220. Fluid testing stick 220 facilitates thepreparation of a fluid sample and/or the sensing of the fluid sample ata low cost and with a low degree of complexity. Fluid testing stick 220includes upper body 224, controller 228, communication interface 232,lower body 234, partition 236, lid 238, fluid interactor substrate 240and fluid interaction elements 244.

Upper body 224 extends on one side of partition 236 and supportscontroller 228 and communication interface 232. In one implementation,upper body 224 serves as a handle for stick 220.

Controller 228 includes circuitry, such as an application-specificintegrated circuit, that controls fluid interaction elements 244. In oneimplementation, controller 228 may comprise hardware in the form of aprocessing unit that follows instructions contained in softwaresupported by upper body 224 or communicated to controller 228 throughcommunication interface 232. In some implementations, controller 228 maybe omitted, wherein fluid interaction elements 244 are controlled bysignals received through communication interface 232 from a remotecontroller or remote electronic device.

Communication interface 232 facilitates communication with controller228. In one implementation, communication interface 232 facilitates awired connection. For example, in one implementation, communicationinterface 232 may comprise an electrical interconnect or contact pad orpads. In one implementation, communication interface 232 may comprise amale or female port or plug for connection to a separate device,directly or through at least one cable or adapter.

In yet another implementation, communication interface 232 mayfacilitate wireless communication. For example, in one implementation,communication interface 232 may comprise a communication antenna servingas a one-way or two-way wireless transponder. In one implementation,communication interface 232 may comprise an active radio frequency tag.In yet another implementation, communication interface 232 may comprisea passive radio frequency tag. In still other implementations,communication interface 232 may communicate via Bluetooth or in otherwireless communication manners.

In some implementations, communication interface 232 may be omitted suchas where controller 228 carries out analysis and testing and directlyindicates results on stick 220. For example, in one implementation,stick 220 may additionally comprise an indicator 245 (shown in brokenlines) supported by upper body 224 and in communication with controller228. In one implementation, the indicator 245 may comprise at least onelight emitting diode which is illuminated by controller 228 based uponthe testing results. In such an implementation, indicator 245 may alsoindicate a current status of the testing process or test being carriedout.

Lower body 234 extends on a second opposite side of partition 236. Lowerbody 234 supports fluid interactor substrate 240 and fluid interactionelements 244. Lower body 234 further cooperates with lid 238 to form afluid chamber 250 extending adjacent to fluid interaction elements 244.In the example illustrated, lower body 234 is formed as a singleintegral unitary body with upper body 224, wherein partition 236 wrapsabout a junction of upper body 224 and lower body 234. In otherimplementations, lower body 234 and upper body 224 may comprise separatestructures which are mounted, welded, fastened or otherwise joined toone another.

In the example illustrated, lower body 234 includes an elongate recess252 in which fluid interactor substrate 240 is located. As shown by FIG.4, recess 252 includes a floor 254 and sidewalls 256. Sidewalls 256project from floor 254 and support lid 238. Sidewalls 256 space portionsof lid 238 above floor 254 to form fluid chamber 250.

Partition 236 extends between upper body 224 and lower body 234.Partition 236 separates controller 228 and communication interface 232from lower portions of stick 220 which may come into contact with afluid sample being diagnosed. In the example illustrated, partition 236includes a seal 260 in the form of a rubber or elastomeric gasket whichis sized and shaped to interact with a surrounding adjacent structure.In some implementations, the seal 260 is sized and shaped to abut andseal against the interior surfaces of a test tube or other receptaclewhich may be used to contain the fluid sample and/or which may form asufficient seal about chamber 250 and fluid interaction elements 244 toinhibit contamination of such components prior to use of stick 220. Inyet other implementations, partition 236 may be omitted.

Lid 238 includes structure that cooperates with lower body 234 to formchamber 250. In the example illustrated, lid 250 includes a flat panelsupported by sidewalls to 56 of lower body 234. In otherimplementations, lid 238 may itself comprise downwardly projectingsidewalls that space a ceiling or roof 264 of lid 238 further from floor254. In one implementation, lid 238 may be formed from a transparentmaterial to form an at least partially transparent chamber to facilitateviewing of the fluid sample within an along a length of channel 250, tofacilitate use with an off-tool/off-chip optical sensor, or to serve asa light transmitting light pipe. In one implementation, lid 238 may beformed from a transparent material such as glass or a transparentpolymer. In other implementations, lid 238 may be formed from othermaterials or may be opaque. For example, electrical detection maybenefit from an opaque lid or opaque chamber.

As shown by FIG. 3, lid 238 terminates prior to reaching end wall 262 ofrecess 252, forming an opening or inlet 264 into the space between lowerbody 234 and lid 238 that forms chamber 250. The edge of inlet 264 maybe angled or straight. As shown by FIG. 4, chamber 250 forms a first gap270 extending from inlet 264 along the length of substrate 240 and theseries of interaction elements 244 and a second smaller gap 272 betweenan upper surface of substrate 240 and interaction elements 244. In oneimplementation, gap 272 is no greater than 1 mm while gap 270 is atleast 50% larger than gap 272. In one implementation, gap 270 is atleast 1.5 mm.

In one implementation, the gap 270 is adjacent to interior surfaces 271formed from a material that is completely wetted with the fluid beingdrawn up. In other words, the gap 270 has surfaces formed from amaterial that is fluid philic with respect to the fluid that is beingdrawn up. In one implementation, the surfaces defining gap 270 comprisea material such as polyetherimide (PEI), or liquid-crystal-polymer(LCP). In some implementations, the surfaces 271 adjacent gap 270 may beformed by an over molded material. For example, in some implementations,material forming lower body 234 may be formed from a first material,wherein the interior surfaces 271 adjacent gap 270 of chamber 250 may beformed from a second different material, coated upon the first material.In some implementations, the interior surfaces 271 may be coated with ametal such as gold. In one implementation, the lower body 234 may befabricated out of an injectable moldable plastic, wherein a layer ofmetal (hydrophilic relative to plastic such as polypropylene) iselectrolitically plated over the plastic. In another implementation thelower body 234 may be fabricated out of an injectable moldable plastic,wherein a layer of metal (hydrophilic relative to plastic such aspolypropylene) is electrolytically plated over the plastic. In someimplementations, the interior surface 271 of chamber 250 may be formedfrom other less hydrophilic materials such as polypropylene.

The mouth or inlet 264 may have a diameter of less than or equal to thecapillary length of the fluid to be drawn up through capillary action.In one implementation, inlet 264 may have an opening dimension of lessthan or equal to 6 mm (based upon the capillary length of water).

In other implementations, the size of inlet 264 is one that provides forcapillary rise (pursuant to Jurin's law) within and along the chamber250, from inlet 264 to all of the fluid interaction elements 244 oflower body 234. In other implementations, inlet 264 may be larger wherepumps may be utilized to draw fluid from to assist the flow of thefluid, initially drawn up through capillary forces.

Fluid interactor substrate 240 includes at least one structure uponwhich fluid interaction elements 244 are provided or supported. In oneimplementation, fluid interactor substrate 240 includes a series ofmicrochips upon which electrical wiring or electrical traces are formedfor connection of controller 228 and/or communication interface 232 tothe individual interaction elements 244. In one implementation,substrate 240 includes an elongate bar, strip or sliver that supportsthe individual interaction elements and which further supports orencloses electrical wiring or electrical traces for connection ofcontroller 228 and/or communication interface 232 to the individualinteraction elements 244.

In one implementation, each microchip or the elongate microchip sliveris formed from silicon. In other implementations, substrate 240 may beformed from other materials, such as glass, ceramics or other dielectricor semi-conductive materials. In the example illustrated, substrate 240is welded, bonded or fastened to floor 254 of lower body 234. In yetother implementations, substrate 240 may be integrally formed as asingle unitary body out of the same material as lower body 234.

Fluid interaction elements 244 comprise elements similar to fluidinteraction elements 24 described above. Fluid interaction elements 244interact with fluid that extends within gap 272. Fluid interactionelements 244 are supported by substrate 240 opposite to gap 272. In oneimplementation, fluid interaction elements 244 extend along an exteriorface of substrate 240. In other implementations, fluid interactionelements 24 or may be recessed or embedded within substrate 240, below aface of substrate 240 that faces lid 238. Each fluid interaction element244 is electrically connected to controller 228 and/or communicationinterface 232 using wiring or traces extending on the surface orembedded within substrate 240.

Although stick 220 is illustrated as comprising nine equidistantly andserially spaced fluid interaction elements 244, in otherimplementations, stick 220 may include a greater or fewer of such fluidinteraction elements 244. Fluid interaction elements 244 may haveuniform or nonuniform spacings along the length of lower body 234. Insome implementations, fluid interaction elements 244 may be arranged inmultiple parallel rows or columns of fluid interaction elements thatextend along the length of lower body 234.

In one implementation, fluid interaction elements 244 thermally interactwith the fluid within gap 272 by altering a temperature of the fluidwithin gap 272. In one implementation, fluid interaction elements 244comprise thermal resistors which generate heat in response to an appliedelectrical current. In such an implementation, fluid interactionelements 244 may facilitate thermal cycling, such as in a nucleic acidtesting or PCR process.

In one implementation, fluid interaction elements 244 may interact withthe adjacent portions of the fluid sample in other fashions. Forexample, in other implementations, fluid interaction element 244 mayeach comprise at least one light emitter. In one implementation, fluidinteraction elements 244 may each comprise a surface that interacts withthe fluid sample to facilitate sensing of the fluid sample. For example,in one implementation, fluid interaction elements 244 may each comprisea plasmonic surface that facilitates surface enhanced Ramanspectroscopy. In one implementation, fluid interaction elements 244 mayeach comprise an array of flexible nano pillars or nano fingers havingplasmonic tips.

In one implementation, fluid interaction elements 244 may comprisemultiple types of fluid interaction elements. For example, in oneimplementation, fluid interaction elements 244 may comprise a first setof thermal fluid interaction elements that heat and/or cool the adjacentfluid and a second set light emitters. In one implementation, fluidinteraction element 244 may comprise a first set of such thermal fluidinteraction elements and a second set of temperature sensing fluidinteraction elements, optical sensing fluid interaction elements and/orfluid presence sensing fluid interaction elements. In yet anotherimplementation, fluid interaction elements 244 may comprise a first setof thermal fluid interaction elements, a set of temperature sensingfluid interaction elements, optical sensing fluid interaction elementsand/or fluid presence sensing fluid interaction elements, and a thirdset of light-emitting fluid interaction elements. The different types offluid interaction elements may be interspersed with one another, thedifferent types arranged in a side-by side fashion or in an alternatingserial fashion along a length of lower body 234.

As shown by FIG. 3, in the example illustrated, fluid interactionelements 244 are serially spaced along a length of a single sliversubstrate 240. The different fluid interaction elements 244 may eachform a different “zone” for control and/or sensing. For example, thedifferent fluid interaction elements 244 may form a column or row ofzones extending parallel to the length (major dimension) of lower body234 and substrate 240.

In one implementation, controller 228 (or a remote controller incommunication with stick 220 via interface 232) may utilize each of acombination of different fluid interaction elements 244 to carry out afluid interaction process. In one implementation, inlet 264 may besubmersed within or may otherwise receive a fluid sample to be diagnosedsuch that fluid is wicked through capillary action along chamber 250towards upper body 224. As the fluid progresses within chamber 250towards upper body 224 along the length of lower body 234, the fluid maybe brought into contact with different fluid presence sensors spacedalong the length of lower body 234, wherein the fluid presence sensors(such as spaced electrodes for which an electrical circuit is completedby the presence of the intervening fluid) indicate to controller 228 (ora remote controller) the extent of fluid wicking and what fluidinteraction elements 244 are submersed within the sample fluid.

In response to receiving signals from such fluid presence sensorsindicating that a particular fluid interaction element 244 is submersedin the fluid, the controller 228 (or remote controller) may outputcontrol signals activating thermal fluid interaction elements that aresubmersed. In one implementation, the fluid interaction elements mayalso include temperature sensors, wherein signals from the temperaturesensors are communicated to controller 228 (or the remote controller)and wherein the controller 228 (or remote controller) adjusts andcontrols the operation of the thermal fluid interaction elements basedupon the sensed temperatures received from the individual temperaturesensing fluid interaction elements. In one implementation, controller228 (or the remote controller) may utilize signals from the temperaturesensing fluid interaction elements to selectively activate the thermalheater fluid interaction elements so as to thermal cycle the samplefluid, such as for a PCR process. In one implementation, controller 228(or the remote controller) may differently heat the fluid in thedifferent zones provided by the independently controllable andactivatable thermal fluid interaction elements.

FIGS. 5-12 are sectional views illustrating portions of example testingsticks 320-1020. Each of the example testing sticks 320-1020 is similarto testing stick 220 except that testing sticks 320-1020 has a differentelongate lower body and lid forming a chamber. The illustrated lowerbodies, lids and substrate 240 of the various sticks uniformly extendalong the length of their respective lower bodies towards partition 236and upper body 224 (shown in FIG. 3). Those portions of testing sticks320-1020 which are not shown in FIGS. 5-12, upper body 224, controller228, communication interface 232, indicator 245 and partition 236, areshown in FIG. 3. Similar to testing stick 220, each of testing sticks320-1020 forms an elongate chamber that has an open lower and with aninlet through which fluid may be wicked up and along the length of thelower body of the testing stick towards upper body 224. FIGS. 5-12 aresectional views with each view taken along a line similar to line 4-4 ofFIG. 3.

FIG. 5 is a sectional view illustrating a portion of an example testingstick 320. Testing stick 320 is similar to testing stick 220 except thattesting stick 320 includes lower body 334 in lieu of lower body 234.Lower body 334 is similar to lower body 234 except a lower body 234additionally includes pedestal 374 which projects from floor 254 toelevate substrate 240 and fluid interaction elements 244 above floor254. As a result, the chamber 350 formed by lower body 334 and lid 238forms a first gap 370 and a second gap 372. Gap 370 may be greater thanthe thickness of substrate 240 for enhanced fluid wicking. At the sametime, pedestal 374 may reduce the size of gap 372 for a larger fluidinteraction element surface area to fluid volume ratio.

FIG. 6 is a sectional view illustrating a portion of an example testingstick 420. Testing stick 420 is similar to testing stick 320 except thatsubstrate 240 and it supported fluid interaction elements 244 aresupported by lid 238 opposite pedestal 374. In the example illustrated,substrate 240 and fluid interaction elements 244 are embedded in theceiling 264 of lid 238 such that fluid interaction elements 244 areflush with the ceiling 268. In other implementations, substrate 240 mayproject below ceiling 268 or may be recessed within ceiling 268 suchthat fluid interaction element 244 also project below ceiling 268 or arerecessed within ceiling 268. In one implementation, gap 372 is nogreater than 1 mm while gap 370 is at least 50% larger than this gap372. In one implementation, gap 370 is at least 1.5 mm.

FIG. 7 is a sectional view illustrating a portion of an example testingstick 520. Testing stick 520 is similar to testing stick 220 except thattesting stick 520 includes lower body 534 and ceiling 538. Lower body534 includes a generally flat panel supporting substrate 240 and fluidinteraction elements 244. In the example illustrated, substrate 240 isembedded within lower body 534 such that fluid interaction elements 244are flush or level floor 254. In other implementations, substrate 240and fluid interaction elements 244 may project above floor 254 or berecessed below 254.

Lid 538 cooperates with lower body 534 to form cavity 550. Lid 538includes ceiling 564, sidewalls 566 and protuberance 568. Ceiling 564extends opposite to floor 254 forming gap 570 through which fluid iswith into and along channel 550. Ceiling 564 terminates at a lower endof lower body 234 forming an inlet 264 through which fluid may enter gap570. Sidewalls 566 extend between floor 254 of lower body 534 andceiling 5642 support in space ceiling 564 opposite to floor 254.Protuberance 568, structurally similar to a stalagmite, projects fromceiling 564 towards floor 254 opposite to substrate 240 and fluidinteraction elements 244. The lower surface of protuberance 568 isspaced from fluid interaction elements 244 so as to form the smaller gap572 that extends opposite to fluid interaction elements 244. In oneimplementation, gap 572 is no greater than 1 mm while gap 570 is atleast 50% larger than this gap 572. In one implementation, gap 570 is atleast 1.5 mm.

FIG. 8 is a sectional view illustrating a portion of an example testingstick 620. Testing stick 620 is similar to testing stick 520 except thatsubstrate 240 and the supported fluid interaction elements 244 aresupported by protuberance 568 of lid 538 opposite fluid interactionelements 244. In the example illustrated, substrate 240 and fluidinteraction elements 244 are embedded in the protuberance 568 of lid 238such that fluid interaction elements 244 are flush with the bottom ofprotuberance 568. In other implementations, substrate 240 may projectbelow the bottom protuberance 568 or may be recessed within protuberance568 such that fluid interaction element 244 also project belowprotuberance 568 or are recessed within protuberance 568.

FIG. 9 is a sectional view illustrating a portion of an example testingstick 720. Testing stick 720 is similar to testing stick 520 describedabove except that testing 720 includes lower body portion 334. Asdescribed above, lower body portion 334 includes pedestal 374 whichelevates and supports substrate 240 and fluid interaction elements 244.As shown by FIG. 9, sidewalls 256 and 566, together, space ceiling 564from floor 254 to form gap 770 through which fluid is whipped into andalong chamber 750. Pedestal 374 supports fluid interaction elements 244below and opposite to the lower surface of protuberance 568 opposite tothe formed gap 772 which is smaller than gap 770. In one implementation,gap 772 is no greater than 1 mm while gap 770 is at least 50% largerthan this gap 772. In one implementation, gap 770 is at least 1.5 mm.

FIG. 10 is a sectional view illustrating portions of an example testingstick 820. Testing stick 820 is similar to testing stick 720 except thatsubstrate 240 and the supported fluid interaction elements 244 aresupported by protuberance 568 of lid 538 opposite fluid interactionelements 244. In the example illustrated, substrate 240 and fluidinteraction elements 244 are embedded in the protuberance 568 of lid 238such that fluid interaction elements 244 are flush with the bottom ofprotuberance 568. In other implementations, substrate 240 may projectbelow the bottom protuberance 568 or may be recessed within protuberance568 such that fluid interaction element 244 also project belowprotuberance 568 or are recessed within protuberance 568.

FIG. 11 is a sectional view illustrating portions of an example testingstick 920. Testing stick 920 is similar to is similar to testing stick720 described above except that testing stick 9220 additionally includesa fluid interactor substrate 940 and fluid interaction elements 944.Those remaining components of stick 920 which correspond to componentsof stick 720 are numbered similarly.

Fluid interactor substrate 940 is similar to fluid interactor substrate240 described above. Likewise, fluid interaction elements 944 aresimilar to fluid interaction elements 244 described above. Fluidinteractor substrate 940 is similar to fluid interactor substrate 240and fluid interaction elements 244 of testing stick 820 in thatsubstrate 944 and fluid interaction elements 944 are supported byprotuberance 568 opposite to pedestal 374. However, as shown by FIG. 11,pedestal 374 also supports fluid interactor substrate 240 and fluidinteraction elements 244 opposite to fluid interactor substrate 940 andfluid interaction elements 944. As a result, fluid within gap 772 may beinteracted upon from both above and below gap 772.

In one implementation, the fluid interaction elements 244, 944 directlyopposite to one another are of the same type of fluid interactionelements. For example, one implementation, the fluid interactionelements directly opposite to one another are both thermal resistorssuch as the fluid within gap 772 may be heated from both above and belowgap 772. In other implementations, the fluid interaction elementsdirectly opposite to one another may be of different types. For example,in one implementation, one of the fluid interaction elements 244, 944may comprise a heater or thermal resistor whereas the other of the fluidinteraction wants 244, 944 may comprise a sensor, such as a temperaturesensor. The close proximity of the temperature sensor to the thermalresistor provides enhanced close loop feedback control over the heatingof the fluid within gap 772. In yet another implementation, one of thefluid interaction elements 244, 944 may comprise a plasmonic surface,such as SERS nano pillars having plasmonic tips while the other of thedirectly opposite fluid interaction elements 244, 944 may comprise alight emitter and an optical sensor to sense interactions of the emittedlight with the analyte deposited upon the plasmonic tips of the closednano pillars.

FIG. 12 is a sectional view illustrating portions of an example testingstick 1020. Testing stick 1020 is similar to testing stick 920 exceptthat rather than being embedded within pedestal 374 and protuberance568, substrates 240 and 940 are mounted, bonded or otherwise secured tothe exterior of pedestal 374 and protuberance 568, respectively,opposite to one another so as to form gap 1072 which may be smaller thangap 772. For the remaining elements of testing stick 1020 whichcorrespond to components of testing stick 920 are numbered similarly.

Although each of testing sticks 220-1020 are illustrated as havingchambers and gaps that have a uniform size axially along the length ofthe lower body of each of the respective sticks, in otherimplementations, each of testing sticks 220-1020 may have at least onetapering dimension, a dimension that decreases in size as the chamberextends away from inlet 264. In such implementations, the taperingdimension or dimensions may further facilitate upward wicking of anysample fluid so as to place a greater number of the fluid interactionelements 244 in contact with the fluid being diagnosed. Although each ofthe gaps opposite to the fluid interaction element is illustrated ashaving a uniform size axially along the length of the lower bodies ofthe various testing sticks, in other implementations, different fluidinteraction elements may be located opposite to differently sized gapsto enhance the performance of the particular fluid interaction elements.

FIGS. 13 and 14 illustrate portions of an example testing stick 1120.FIGS. 13 and 14 illustrate those portions of testing stick 1120 belowpartition 236. Upper body portion 224, controller 228, communicationinterface 232 and indicator 245, each of which are part of testing stick1120, are shown in FIG. 3. As shown by FIGS. 13 and 14, the lowerportion of testing stick 1120 is similar to the lower portions oftesting stick 220 except that testing stick 1120 includes a lower bodyportion 1134 which has an upwardly inclined floor 1154 on opposite sidesof substrate 240. Those remaining components of lower body portion 1134which correspond to components of lower body portion 234 are numberedsimilarly.

Floor 1154 inclines as it extends away from inlet 264 towards upper bodyportion 224 (shown in FIG. 3). As a result, while gap 272 remainsuniform in size, gap 270 gradually reduces in size as it approachesupper body portion 224 (shown in FIG. 3). The interior volume of chamber250 decreases as it extends away from inlet 264 to provide enhancedwicking or capillary movement of fluid along chamber 1150.

FIGS. 15 and 16 illustrate portions of an example testing stick 1220.FIGS. 15 and 16 illustrate those portions of testing stick 1120 belowpartition 236. Upper body portion 224, controller 228, communicationinterface 232 and indicator 245, each of which are part of testing stick1220, are shown in FIG. 3. As shown by FIGS. 15 and 16, the lowerportion of testing stick 1220 is similar to the lower portions oftesting stick 220 except that testing stick 1220 includes a lid 1238which has a declining floor 1254 on opposite sides of substrate 240.Those remaining components of lid 1238 which correspond to components oflid 238 are numbered similarly.

Floor 1254 declines as it extends away from inlet 264 towards upper bodyportion 224 (shown in FIG. 3). As a result, while gap 272 remainsuniform in size, gap 274 gradually reduces in size as it approachesupper body portion 224 (shown in FIG. 3). The interior volume of chamber250 decreases as it extends away from inlet 264 to provide enhancedwicking or capillary movement of fluid along chamber 1250.

FIG. 17 is a sectional view of portions of an example testing stick 1320take along a sectional line similar to the sectional line 14-14 takenthrough testing stick 1120. FIG. 17 illustrates those portions oftesting stick 1320 below partition 236. Upper body portion 224,controller 228, communication interface 232 and indicator 245, each ofwhich are part of testing stick 1320, are shown in FIG. 3. Testing stick1320 is similar to testing stick 1120 except that testing 1320 includesfluid interactor substrate 1340 in place of substrate 240.

Fluid interactor substrate 1340 is similar to fluid interactor substrate240 except that fluid interactor substrate 1340 ramped upward or isinclined as it approaches upper body portion 224 (shown in FIG. 3).Fluid interactor substrate 1340 includes an upwardly inclined topsurface 1354 that gradually approaches and becomes closer to ceiling 264of lid 238 as it extends away from inlet 264 towards upper body portion224. Top surface 1354 supports fluid interaction elements 244 atdifferent spacings, opposite differently dimensioned gaps 272, withrespect to ceiling 238. In the example illustrated, substrate 1340supports fluid interaction element 244A opposite a gap 272A, supportsfluid interaction element 244B opposite a gap 272B smaller than gap272A, supports fluid interaction element 244C opposite a gap 272Csmaller than gap 272B, supports fluid interaction element 244D oppositea gap 272D smaller than gap 272C, supports fluid interaction elements244E opposite a gap 272E smaller than gap 272D and supports fluidinteraction element 244F opposite a gap 272F smaller than gap 272E. Inthe example illustrated, fluid interaction elements 272A, 272B and 272Care spaced from one another along substrate 1354 by a first distancewhereas fluid interaction element 272D, 272E and 272F are spaced fromone another by different distances along substrate 1354. In the exampleillustrated, the different dimensions for the different gaps 272A-272Fprovide different fluid interaction element surface area to volumeratios to enhance the performance of the particular fluid interactionelements. Although testing 1320 is illustrated as comprising six fluidinteraction elements 244, it should be appreciated that testing stick1320 may comprise a greater or fewer of such fluid interaction elements244 at other relative serial spacings and/or in side-by-sidearrangements.

FIGS. 18 and 19 illustrate portions of an example testing stick 1420.FIGS. 18 and 19 illustrate those portions of testing stick 1420 belowpartition 236. Upper body portion 224, controller 228, communicationinterface 232 and indicator 245, each of which are part of testing stick1420, are shown in FIG. 3. As shown by FIGS. 18 and 19, the lowerportion of testing stick 1420 is similar to the lower portions oftesting stick 1120 except that testing stick 1420 includes lower body1434 and fluid interactor substrate 1440 in place of lower body 1134 andfluid interactor substrate 240. Those remaining components of testingstick 1420 which correspond to components of testing stick 1120 arenumbered similarly.

Lower body 1434 is similar to lower body 1134 described above exceptthat lower body 1434 includes converging sidewalls 1456 in place ofsidewalls 256. Converging sidewalls 1456 converge towards one another asthey extend away from inlet 264, as they extend towards upper body 224(shown in FIG. 3). As a result, while gap 272 remains uniform in size,the width of gap 274 gradually reduces in size as it approaches upperbody portion 224 (shown in FIG. 3). The interior volume of chamber 1450decreases as it extends away from inlet 264 to provide enhanced wickingor capillary movement of fluid along chamber 1450.

Fluid interactor substrate 1440 is similar to fluid interactor substrate240 except that fluid interactor substrate 1440 includes differentlysized substrate risers 1480A, 1480B, 1480C, 1480D, 1480E and 1480F(collectively referred to as substrate risers 1480). Risers 1480 havedifferent heights, supporting their respective fluid interactionelements 244 opposite different gaps with respect to lid 238. In theexample illustrated, each of pedestals 1480 supports multiple fluidinteraction elements in a side-by-side layout or in a serial layout. Asa result, different types of fluid interaction elements may be supportedopposite to differently dimension gaps most suited for the particulartype of fluid interaction element. In the example illustrated, risers1480A, 1480B, 1480C, 1480D, 1480E and 1480F support sets of fluidinteraction elements 244A, 244B, 244C, 244D, 244E and 244F opposite todifferently dimension gaps 272A, 272B, 272C, 272D, 272E and 272F,respectively. Although testing stick 1420 is illustrated as comprisingsix risers supporting six different sets of fluid interaction elements244, in other implementations, testing stick 1420 may comprise differentnumbers of risers 1480 at alternative spacings and different numbers ofsets of fluid interaction elements 244 having different arrangements ordifferent numbers.

FIGS. 13-19 illustrate various lower bodies, lids and substrates thatprovide tapering volumes that facilitate wicking of fluid away frominlet 264 and that provide differently dimension gaps opposite to fluidinteraction elements. Although each of such features is illustrated asbeing applied to a lower body similar to lower body 234 shown in FIG. 4,it should be appreciated that each of the various features shown inFIGS. 13-19 may be applied individually or in combination with otherfeatures to each of the lower body shown in FIGS. 5-12. For example,each of the lower bodies shown in FIGS. 5-12 may have incline floor 1154in place of floor 254. Each of the lids shown in FIGS. 5-12 may have adeclined ceiling 1254 on opposite sides of the gap that is itselfopposite to the fluid interaction elements. Each of the substratesand/or each of the pedestals 374 supporting the substrates may beinclined similar to substrate 1340. Each of the sidewalls of the lowerbodies and/or the lids shown in FIG. 5-12, where provided, may haveconverge similar to sidewalls 1456. Each of the substrates shown inFIGS. 5-12 may comprise substrate risers of the same or differentheights spaced along the axial length of the lower bodies to providedifferently sized gaps opposite to the fluid interaction elements. Eachof the pedestals 374 and each of the protuberances 568 shown in FIGS.5-12 may have spaced risers, similar to the risers of substrate 1440,that provide different dimensions for different gaps opposite todifferent sets or individual fluid interaction elements. In each of thetesting stick shown in FIG. 13-19, additional fluid interaction elementsmay be provided and supported on the opposite sides of the smaller gaps272, opposite to the illustrated fluid interaction elements 244. In eachof the illustrated fluid testing sticks, the interior surfaces of thechambers, such as the floors and ceilings opposite the larger gaps 270may be formed from or may be coated or laminated with different fluidwetting materials that are fluid philic, such as the fluid philic layermaterial 271 shown in FIG. 4 to further facilitate wicking (capillarymovement) of the fluid into and along the respective chambers.

FIG. 20 illustrates an example testing stick 1520. Testing stick 1520 issimilar to testing stick 220 described above except that testing stick1520 includes lid 1538 and light emitter 1582. Those remainingcomponents of testing stick 1520 which correspond to components oftesting stick 220 are numbered similarly.

Lid 1538 is similar to lid 238 set that lid 1538 is not supported bysidewalls to 56 of lower body 234, but rest within recess 252 upon floor254. As shown by FIG. 21, lid 1538 includes an elongate channel 1584forming ceiling 264 of lid 1538. Ceiling 264 spaced above floor 254 andabove substrate 240 (and fluid interaction elements 244) by sidewalls1586 of lid 1538 which extend an opposite side of channel 1584.Sidewalls 1586 and ceiling 264 increase in size as they extend away frominlet 264 towards light emitter 1582. In the example illustrated, thesize of channel 264 and the size of the gap opposite to fluidinteraction elements 244 remains the same along the length of substrate240. In other implementations, as described above with respect totesting sticks 1320-1420, the gap opposite the different fluidinteraction element 244 may vary from one fluid interaction element toanother fluid interaction element. For example, in otherimplementations, the height of channel 264 may gradually ramp up or downto vary the gap dimension along lid 1538. In another implementation, lid1538 may include differently dimensioned protuberances 568 (shown inFIG. 7), protuberances that have different heights so as to project intodifferent proximities to the upper surface of substrate 240 and fluidinteraction elements 244 along the length of channel 264 and opposite todifferent fluid interaction elements, providing such fluid interactionelements with differently sized opposing fluid gaps along the length ofchannel 264.

Light emitter 1582 is supported by lower body 234 and is located at theenlarged end of lid 1538. Light emitter 1582 serves as a backlight,transmitting light through the transparent material lid 1538, whichserves as a light pipe, to each of the fluid interaction elements 244along the length of testing stick 1520. The nonuniform thickness of lid1538 with the increasing thickness of ceiling 264 and sidewalls 156towards light emitter 1582 (the angling of lid 1538) enhances lighttransmission efficiency by lid 1538 along substrate 240. In oneimplementation, light emitter 1582 includes a light emitting diode thatprovides RGB (red green blue) backlight controlled by controller 228.

FIGS. 22-24 illustrate one example use of testing stick 1520. As shownby FIG. 22, testing stick 1520 may be stored for use with its lower endcontained within a tubular receptacle 1600. Seal 260 contacts and sealsagainst the interior side surfaces of receptacle 1600, inhibitingcontamination of the lower portions of testing stick 1520.

As shown by FIG. 23, stick 1520 may be temporarily removed fromreceptacle 1600 and a sample to be diagnosed may be placed withinreceptacle 1600. In some implementations, other reagents and/or markers(such as fluorescent markers or tags) may additionally be depositedwithin receptacle 1600. Thereafter, testing stick 1520 may be reinsertedinto receptacle 1600 such that inlet 264 is at or below the top or level1604 of the sample mixture 1606 within receptacle 1600. Due to thedimensioning of inlet 264 (as described above) as well as thedimensioning of gap 272 (shown in FIG. 4), the sample mixture or analyteis drawn or whipped upward through the larger gap 270 through capillaryforces (no other pumps being utilized). As a sample mixture 1606 isdrawn up through gap 270, the sample mixture 1606 also flows into andacross the smaller gap(s) 272 that extend opposite to the fluidinteraction elements 244.

As described above, in some implementations, some of the fluidinteraction elements 244 may comprise fluid presence sensors, such aselectrode pairs for which an electrical circuit is completed by theintervening fluid. Such fluid presents sensors may output signals tocontroller 228 (or a remote controller) indicating the extent of fluidwicking along substrate 240. Based upon such signals, controller 228 (ora remote controller) may output control signals activating differentfluid interaction element 244 as a fluid is with long substrate 240.

In some implementations, fluid interaction element 244 may comprisedifferent combinations of multiple different types of fluid interactionelements. For example, in one implementation, fluid interaction element244 may comprise photo sensors, such as photodiodes and thermalresistive heaters. In such an implementation, controller 228 may outputcontrol signals causing those fluid interaction elements 244 which arethermal resistive heaters to thermal cycle the sample mixture 1606 suchas according to a nucleic acid sensing protocol or PCR protocol.Controller 228 may subsequently output control signals activating lightemitter 1582 to illuminate the mixture 1606 which absorbs one wavelengthof light and emits light at another wavelength of light based upon asignaling molecule in the mixture 1606, wherein the re-emitted light issensed by those fluid interaction elements 244 that are in the form ofoptical sensors, such as photodiodes. In other implementations, othercolor or light generating reactions (for example, bioluminescence,particle movement (light/dark), ink properties, enzyme-linkedimmunosorbent assay (ELISAs)) may be carried out using those fluidinteraction element(s) 244 that comprise optical sensors, such asphotodiodes.

As shown by FIG. 24, testing stick 1520 may communicate with a remotecontroller or a remote/separate electronic device 1700 usingcommunication interface 232. In the example illustrated, the electronicdevice 1700 includes a smart phone, wherein interface 232 includes anelectrical interconnect that plugs into a port 1704 of the smart phone1700. During such connection, control signals may be transmitted fromdevice 1700 to testing stick 1520. Sensed data may be transmitted fromtesting stick 1520 to device 1700. Device 1700 may display on-screen1702 the results of the diagnosis based upon sample 1606. Thereafter,testing stick 1520 may be discarded or may be stored within receptacle1600 and with the original sample 1606.

In other implementations, testing stick 1520 may communicate with aseparate electronic device in other fashions. As described above, inother implementations, testing stick 1520 may communicate in a wirelessfashion. Testing stick 1520 may communicate in a wired fashion throughother communication interfaces, either directly or through anintermediate cable. In some implementations, the interaction and sensingof the fluid by the fluid interaction elements 244 may occur while sick15/20 connected or in communication with the electronic device 1700.

As should be appreciated, testing stick 1520 may have a variety ofdifferent architectures. Testing stick 1520 may alternatively compriseany of the architectures shown and described above with respect to thelower portions of the other example testing sticks shown in FIGS. 3-19.Although each of such testing sticks is illustrated as wicking a samplefluid or analyte from the lower end of lower body 234 through inlet 262,in other implementations, each of such testing sticks may alternativelywick fluid through capillary action through side ports extending throughside walls of the formed chambers or through top or bottom portsextending through the lower bodies or the lids.

Although the present disclosure has been described with reference toexample implementations, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the scopeof the claimed subject matter. For example, although different exampleimplementations may have been described as including features providingbenefits, it is contemplated that the described features may beinterchanged with one another or alternatively be combined with oneanother in the described example implementations or in other alternativeimplementations. Because the technology of the present disclosure isrelatively complex, not all changes in the technology are foreseeable.The present disclosure described with reference to the exampleimplementations and set forth in the following claims is manifestlyintended to be as broad as possible. For example, unless specificallyotherwise noted, the claims reciting a single particular element alsoencompass a plurality of such particular elements. The terms “first”,“second”, “third” and so on in the claims merely distinguish differentelements and, unless otherwise stated, are not to be specificallyassociated with a particular order or particular numbering of elementsin the disclosure.

1. A fluid testing device comprising: a fluid interaction element; and afluid chamber to contain a fluid to be interacted upon by the fluidinteraction element, the fluid chamber forming a first gap through whichfluid is wicked to a second gap in the fluid chamber that is oppositethe fluid interaction element and less than the first gap.
 2. The fluidtesting device of claim 1, wherein the first gap spaces a first interiorsurface of the chamber and a second interior surface of the chamber andwherein the fluid interaction element projects from the first surfacetowards the second surface to form the second gap.
 3. The fluid testingdevice of claim 1, wherein the first gap spaces a first interior surfaceof the chamber and a second interior surface of the chamber and whereinthe chamber further includes a pedestal projecting from the firstsurface and supporting the fluid interaction element opposite the secondgap.
 4. The fluid testing device of claim 3, wherein the fluidinteraction element is at least partially received within the pedestal.5. The fluid testing device of claim 3, wherein the chamber furtherincludes a protuberance projecting from the second surface opposite thefluid interaction element to form the second gap.
 6. The fluid testingdevice of claim 1, wherein the first gap spaces a first interior surfaceof the chamber and a second interior surface of the chamber and whereinthe chamber further includes a protuberance projecting from the secondsurface opposite the fluid interaction element to form the second gap.7. The fluid testing device of claim 6, wherein the fluid interactionelement projects from the first surface towards the second surfaceopposite the protuberance.
 8. The fluid testing device of claim 6,wherein the fluid interaction element is at or below the first surfaceand opposite the protuberance.
 9. The fluid testing device of claim 1,wherein the second gap is no greater than 1 mm and wherein the first gapis at least 50% larger than the second gap.
 10. The fluid testing deviceof claim 1, wherein the first gap is at least 1.5 mm.
 11. The fluidtesting device of claim 1, wherein the fluid interaction element is on afirst side of the second gap, the fluid testing device furthercomprising a second fluid interaction element opposite the second gap ona second side of the second gap opposite the first side.
 12. The fluidtesting device of claim 1, wherein the chamber opposite the second gapis transparent.
 13. The fluid testing device of claim 1, comprising anelongate stick forming the chamber, the chamber having an inletproximate an end of the stick.
 14. A fluid testing method comprising:wicking fluid into a first gap in a chamber of a fluid testing device;and interacting with the fluid with a fluid interaction element whilethe fluid is in a second gap in the chamber that is adjacent the firstgap in the chamber and less than the first gap.
 15. A fluid testingstick comprising: a first end supporting a controller; and a second endforming a fluid interactor, the fluid interactor comprising: a fluidinteraction element under control of the controller; and a fluid chamberto contain a fluid to be sensed by the fluid interaction element, thefluid chamber forming a first gap through which fluid is wicked to asecond gap in the fluid chamber that is opposite the fluid interactionelement and is less than the first gap.
 16. The fluid testing device ofclaim 1, wherein the fluid interaction element is to interact with thefluid while the fluid is in the second gap of the fluid chamber.
 17. Thefluid testing method of claim 14, further including positioning a volumeof the fluid in the second gap and adjacent to the fluid interactionelement.
 18. The fluid testing stick of claim 15, wherein the second gapis to position a volume of the fluid adjacent to the fluid interactionelement and the fluid interaction element is to interact with the volumeof the fluid while the volume is in the second gap of the fluid chamber.